When is the ideal time to spay?

I have a four and half month old Labrador bitch from working lines and have decided to get her spayed. My vet recommends doing this before her first season, which means from the age of five to around seven months old. But this seems really young to me and she is still growing very fast. Could you please give me your opinion or maybe someone that I could get some advice from? Many thanks.
Carol by email

Contentious topic! As a practice, we routinely spay before a first season, provided the external genitalia are well developed; otherwise, we postpone until three-and-a half-months after the first season to give any changes associated with a false pregnancy to resolve, giving more time to grow and mature. I would therefore be guided by your veterinary surgeon who will be able to examine your bitch when your she is nearing six months of age and advise you further.
I do know breeders who have their puppies neutered at eight weeks of age, so that the puppies are sold already spayed and castrated.
We had our Labrador Pippin spayed at 5.5 months old. I seem to think she weighed 17.5kg at the time. I had not been aware of being at all worried about the operation until that evening, when she was lying in front of the fire, I remember feeling relieved that it was all over – there would be no need to worry about spotting her coming into season, and whether it would be whilst we were away camping. Not easy to confine a bitch in season away from amorous males whilst staying under canvas!
Pippin certainly made a rapid recovery. The next morning, she was so bright, bouncing around and wanting to go out for her usual walk. I did give her follow-up doses of a non-steroidal anti-inflammatory drug for pain-relief, but it was very hard to keep her quiet whilst she was healing up!
Since then, Pippin has matured and grown as I would have expected, and has not had a problem retaining her waistline. At the moment, she is in fact a little underweight at 23.5kg; she certainly looks better nearer to 25kg. When a bitch is spayed once fully grown, it is advisable to cut back the ration to avoid weight gain through a post-neutering fall in the so-called Basal Metabolic Rate, meaning that the body works at a lower rate and therefore burns off less energy. This is one reason why owners of overweight bitches are advised to work on weight-loss before spaying, in addition to reducing anaesthetic risks. Being spayed whilst still growing, you will continue to change the amount and type of food so, psychologically, I think it is easier to avoid your bitch becoming overweight.
I hope this helps.
Alison Logan, Vet